1. Field of Invention
The present invention relates to a process for preparing a 2,3-dihydro-7-benzofuranol from a 1,3-benzodioxole and to a novel 1,3-benzodioxole utilized in the process. More particularly the invention relates to thermal rearrangement of 2-substituted 1,3-benzodioxoles in the presence of an acid or transition element catalyst to form 2-substituted 2,3-dihydro-7-benzofuranol.
2. Description of the Prior Art
2,3-Dihydro-7-benzofuranols which are substituted at the 2 position are known intermediates for the preparation of benzofuranyl carbamate insecticides such as those set forth in U.S. Pat. Nos. 3,470,299, 3,474,170 and 3,474,171. Several routes are known for preparing these 2,3-dihydro-7-benzofuranols. Some of these are set forth in the foregoing patents and in Franko-Filipasic, U.S. Pat. No. 3,320,286, which discloses a process now in commercial use. In this process for preparing 2,3-dihydro-2,2-dimethyl-7-benzofuranol, o-nitrophenol is first reacted with methallyl halide. The resulting o-methallyloxynitrobenzene is thermally rearranged then cyclized to 2,3-dihydro-2,2-dimethyl-7-nitrobenzofuran. The latter is then successively reduced, diazotized, and hydrolyzed.
The object of the present invention is to provide a more direct route to 2,3-dihydro-7-benzofuranols substituted at the 2 position. It has now been found that these compounds are readily prepared by thermally rearranging a corresponding 2-substituted-1,3-benzodioxole.